ViewPager FragmentPagerAdapter Nullpointer

android fragment android-viewpager
passsy picture passsy · Jun 19, 2012 · Viewed 20.7k times · Source

I got this error by using the ViewPager in the Android Support package. from the Horizontal View Swiping with ViewPager Tutorial

06-19 13:07:25.950: E/AndroidRuntime(16382): FATAL EXCEPTION: main
06-19 13:07:25.950: E/AndroidRuntime(16382): java.lang.NullPointerException
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:347)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:342)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:97)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:649)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.support.v4.view.ViewPager.populate(ViewPager.java:783)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1016)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.View.measure(View.java:12728)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:594)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:376)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.View.measure(View.java:12728)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.View.measure(View.java:12728)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:660)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.View.measure(View.java:12728)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2092)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.View.measure(View.java:12728)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1064)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.os.Looper.loop(Looper.java:137)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at android.app.ActivityThread.main(ActivityThread.java:4424)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at java.lang.reflect.Method.invokeNative(Native Method)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at java.lang.reflect.Method.invoke(Method.java:511)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-19 13:07:25.950: E/AndroidRuntime(16382):    at dalvik.system.NativeStart.main(Native Method)

Answer

Chris Knight picture Chris Knight · Dec 5, 2013

Just in case anyone doesn't read the comments of passsy's answer, here is a summary of the useful answers:

1) Examine your getItem(int index) method very closely and look for any logic, scenarios or missing 'break' statements which might cause you to end up with a null fragment.

2) Check that the count returned by getCount() matches the number of fragments returned in getItem(int index).

3) Examine your imports and ensure you aren't mixing android.app.Fragment with android.support.v4.app.Fragment

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